36 idf webers on a 2l

[thirdbrother3]

I've been looking at very cheap performance from my 2.0 spider
I've got to do the head gasket and it needs a new clutch anyway so budget is very tight.
45 DCOEs would seem to be the route for bolt on power but a pair would double the value of the car!

whilst reading another topic in this section someone mentioned using IDFs out of a 1.5ti alfasud (but said they are rare and also expensive)

Well it just so happens i've had one of said engines in my (various) shed/s for the past 15 years. i've moved house with it twice!

You can imagine then i got all excited and ventured off through the snow to the end of the garden to retrieve the carbs.

Ive since read that IDF's aren't really meant for transverse engines and fuel starvation might be an issue (on cornering), but others said they haven't had too many problems so are i'm willing to try.

I've been reading the Guy Croft bible, and he states a convincing argument to having one barrel of carburettor per cylinder, and puts up a very useful basic jetting guide for side draught carbs but not much for IDFs.

Has anyone fitted 36IDF 's to a standard 2.0 litre engine and if so what was the performance increase. Also what would be a good set up jeting/ chokes wise. (you'll have to go easy on me as i'm new to webbers - last time i did anything with carbs was modifying some SUs on a mini)

any help gratefully received

[75coupe]

Hi,

I would say your first problem would be finding an inlet manifold to suit the Beta, unless you want to make one. The Fiat 124 used twin 40 IDF carbs and manifolds are available, but the engine is upright and the Fiat also used a cam box mounted distributor.
 
The next problem would be jetting. IDF's are very similar to DCOE's and use for the most part the same jets, so this would not be a problem, but where to start would be, I think I have a jetting program somewhere that gives rough settings, I obtained it off the net, so you could do the same.

What size chokes are in the IDF's? I would imagine they are small - no more than 30mm? You really need at least 34mm chokes for a decent upgrade on a 2 litre.

As for the transverse orientation, well all I can say is that I have seen them in use on a Fiat X1/9 prototipo replica which used a 2L Beta engine and box and they worked fine on that in competition! They were 44 IDF's though!

As for how much power you will get with 36 IDF's? Well you wont get anymore than 10 BHP increase (max) at a guess, may be less. The Fiat 124 Spider Abarth 1800 got 128 BHP from 44 IDF's, with the standard 124 1800 having 118BHP on a single twin choke Weber, the carbs and a better exhaust being the only difference.

On a different note, you can get 10 BHP out of a 2 litre by increasing the Compression, but this means higher CR pistons, such as Beta 1600 ones.

It may be better to sell the IDF's and save for some 45 DCOE's, which will give you 18 BHP increase straight away, and the potential to get up to 200 BHP with all the right mods!!!!......Failing that 40 DCOe's will be better than the IDF, but if you can make a manifold, and it does not cost you anything, then go for it, as far as I am concerned, anything is better than the painfull std carb! and twin webers do make the right noise on full song!

[thirdbrother3]

Great response, thank you. certainly food for thought. i was planning on fabricating a manifold. given the estimated power increase, 45's might be a better route or larger down draughts.

i'll look into selling my 36 idfs (popular on beetles apparently)

thanks again